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</pre><pre class="rust"><code><span class="comment">// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
</span><span class="kw">use </span>std::{cell::RefCell, collections::hash_map, env, fs, hash::Hasher, time::SystemTime};
<span class="kw">use </span><span class="kw">super</span>::tz_info::TimeZone;
<span class="kw">use super</span>::{FixedOffset, NaiveDateTime};
<span class="kw">use crate</span>::{Datelike, LocalResult};
<span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>offset_from_utc_datetime(utc: <span class="kw-2">&</span>NaiveDateTime) -> LocalResult<FixedOffset> {
offset(utc, <span class="bool-val">false</span>)
}
<span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>offset_from_local_datetime(local: <span class="kw-2">&</span>NaiveDateTime) -> LocalResult<FixedOffset> {
offset(local, <span class="bool-val">true</span>)
}
<span class="kw">fn </span>offset(d: <span class="kw-2">&</span>NaiveDateTime, local: bool) -> LocalResult<FixedOffset> {
TZ_INFO.with(|maybe_cache| {
maybe_cache.borrow_mut().get_or_insert_with(Cache::default).offset(<span class="kw-2">*</span>d, local)
})
}
<span class="comment">// we have to store the `Cache` in an option as it can't
// be initalized in a static context.
</span><span class="macro">thread_local! </span>{
<span class="kw">static </span>TZ_INFO: RefCell<<span class="prelude-ty">Option</span><Cache>> = Default::default();
}
<span class="kw">enum </span>Source {
LocalTime { mtime: SystemTime },
Environment { hash: u64 },
}
<span class="kw">impl </span>Source {
<span class="kw">fn </span>new(env_tz: <span class="prelude-ty">Option</span><<span class="kw-2">&</span>str>) -> Source {
<span class="kw">match </span>env_tz {
<span class="prelude-val">Some</span>(tz) => {
<span class="kw">let </span><span class="kw-2">mut </span>hasher = hash_map::DefaultHasher::new();
hasher.write(tz.as_bytes());
<span class="kw">let </span>hash = hasher.finish();
Source::Environment { hash }
}
<span class="prelude-val">None </span>=> <span class="kw">match </span>fs::symlink_metadata(<span class="string">"/etc/localtime"</span>) {
<span class="prelude-val">Ok</span>(data) => Source::LocalTime {
<span class="comment">// we have to pick a sensible default when the mtime fails
// by picking SystemTime::now() we raise the probability of
// the cache being invalidated if/when the mtime starts working
</span>mtime: data.modified().unwrap_or_else(|<span class="kw">_</span>| SystemTime::now()),
},
<span class="prelude-val">Err</span>(<span class="kw">_</span>) => {
<span class="comment">// as above, now() should be a better default than some constant
// TODO: see if we can improve caching in the case where the fallback is a valid timezone
</span>Source::LocalTime { mtime: SystemTime::now() }
}
},
}
}
}
<span class="kw">struct </span>Cache {
zone: TimeZone,
source: Source,
last_checked: SystemTime,
}
<span class="attr">#[cfg(target_os = <span class="string">"aix"</span>)]
</span><span class="kw">const </span>TZDB_LOCATION: <span class="kw-2">&</span>str = <span class="string">"/usr/share/lib/zoneinfo"</span>;
<span class="attr">#[cfg(not(any(target_os = <span class="string">"android"</span>, target_os = <span class="string">"aix"</span>)))]
</span><span class="kw">const </span>TZDB_LOCATION: <span class="kw-2">&</span>str = <span class="string">"/usr/share/zoneinfo"</span>;
<span class="kw">fn </span>fallback_timezone() -> <span class="prelude-ty">Option</span><TimeZone> {
<span class="kw">let </span>tz_name = iana_time_zone::get_timezone().ok()<span class="question-mark">?</span>;
<span class="attr">#[cfg(not(target_os = <span class="string">"android"</span>))]
</span><span class="kw">let </span>bytes = fs::read(<span class="macro">format!</span>(<span class="string">"{}/{}"</span>, TZDB_LOCATION, tz_name)).ok()<span class="question-mark">?</span>;
<span class="attr">#[cfg(target_os = <span class="string">"android"</span>)]
</span><span class="kw">let </span>bytes = android_tzdata::find_tz_data(<span class="kw-2">&</span>tz_name).ok()<span class="question-mark">?</span>;
TimeZone::from_tz_data(<span class="kw-2">&</span>bytes).ok()
}
<span class="kw">impl </span>Default <span class="kw">for </span>Cache {
<span class="kw">fn </span>default() -> Cache {
<span class="comment">// default to UTC if no local timezone can be found
</span><span class="kw">let </span>env_tz = env::var(<span class="string">"TZ"</span>).ok();
<span class="kw">let </span>env_ref = env_tz.as_deref();
Cache {
last_checked: SystemTime::now(),
source: Source::new(env_ref),
zone: current_zone(env_ref),
}
}
}
<span class="kw">fn </span>current_zone(var: <span class="prelude-ty">Option</span><<span class="kw-2">&</span>str>) -> TimeZone {
TimeZone::local(var).ok().or_else(fallback_timezone).unwrap_or_else(TimeZone::utc)
}
<span class="kw">impl </span>Cache {
<span class="kw">fn </span>offset(<span class="kw-2">&mut </span><span class="self">self</span>, d: NaiveDateTime, local: bool) -> LocalResult<FixedOffset> {
<span class="kw">let </span>now = SystemTime::now();
<span class="kw">match </span>now.duration_since(<span class="self">self</span>.last_checked) {
<span class="comment">// If the cache has been around for less than a second then we reuse it
// unconditionally. This is a reasonable tradeoff because the timezone
// generally won't be changing _that_ often, but if the time zone does
// change, it will reflect sufficiently quickly from an application
// user's perspective.
</span><span class="prelude-val">Ok</span>(d) <span class="kw">if </span>d.as_secs() < <span class="number">1 </span>=> (),
<span class="prelude-val">Ok</span>(<span class="kw">_</span>) | <span class="prelude-val">Err</span>(<span class="kw">_</span>) => {
<span class="kw">let </span>env_tz = env::var(<span class="string">"TZ"</span>).ok();
<span class="kw">let </span>env_ref = env_tz.as_deref();
<span class="kw">let </span>new_source = Source::new(env_ref);
<span class="kw">let </span>out_of_date = <span class="kw">match </span>(<span class="kw-2">&</span><span class="self">self</span>.source, <span class="kw-2">&</span>new_source) {
<span class="comment">// change from env to file or file to env, must recreate the zone
</span>(Source::Environment { .. }, Source::LocalTime { .. })
| (Source::LocalTime { .. }, Source::Environment { .. }) => <span class="bool-val">true</span>,
<span class="comment">// stay as file, but mtime has changed
</span>(Source::LocalTime { mtime: old_mtime }, Source::LocalTime { mtime })
<span class="kw">if </span>old_mtime != mtime =>
{
<span class="bool-val">true
</span>}
<span class="comment">// stay as env, but hash of variable has changed
</span>(Source::Environment { hash: old_hash }, Source::Environment { hash })
<span class="kw">if </span>old_hash != hash =>
{
<span class="bool-val">true
</span>}
<span class="comment">// cache can be reused
</span><span class="kw">_ </span>=> <span class="bool-val">false</span>,
};
<span class="kw">if </span>out_of_date {
<span class="self">self</span>.zone = current_zone(env_ref);
}
<span class="self">self</span>.last_checked = now;
<span class="self">self</span>.source = new_source;
}
}
<span class="kw">if </span>!local {
<span class="kw">let </span>offset = <span class="self">self
</span>.zone
.find_local_time_type(d.timestamp())
.expect(<span class="string">"unable to select local time type"</span>)
.offset();
<span class="kw">return match </span>FixedOffset::east_opt(offset) {
<span class="prelude-val">Some</span>(offset) => LocalResult::Single(offset),
<span class="prelude-val">None </span>=> LocalResult::None,
};
}
<span class="comment">// we pass through the year as the year of a local point in time must either be valid in that locale, or
// the entire time was skipped in which case we will return LocalResult::None anyway.
</span><span class="self">self</span>.zone
.find_local_time_type_from_local(d.timestamp(), d.year())
.expect(<span class="string">"unable to select local time type"</span>)
.map(|o| FixedOffset::east_opt(o.offset()).unwrap())
}
}
</code></pre></div>
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